Known potentiometers may in addition to a variable resistance function have a built-in switch that provides the option of changing between first and second switch states via the potentiometer knob—typically in an extreme position of the potentiometer knob. The potentiometer may function as a volume control where the potentiometer knob upon turning in one direction decreases the volume, and finally turns off the signal and/or switches off power. Preferably, the user is provided with feedback indicating that the switch has reached an off state, e.g. light in a display or diode, a sound, a tactile mechanical resistance towards turning of the knob, or similar. In relation to volume controls for portable audio equipment feedback is often provided to the user by a tactile feedback upon turning a rotatable volume control knob to or beyond its lowermost position. Hereby, the user has a indication that the device has been switched off so as to save battery without the need for visual confirmation or feedback.
PJ 88 manufactured by the applicant is an example of a potentiometer with a built-in switch providing the user with a tactile feedback. PJ 88 is suited for miniature applications, such as a combined volume control and on/off switch in a hearing aid. PJ 88 provides a combined switch function and tactile feedback arranged by engagement of two metal springs upon interaction with a protrusion on a user rotatable part. The two metal springs are both engaged with the switch function as well as the tactile feedback function.
The combined switch and tactile feedback arrangement provided in PJ 88 has a number of disadvantages that are particularly troublesome with respect to further miniaturisation. The two metal springs are small when compared to an overall size of the potentiometer assembly. This means that the solutions are not suited for further miniaturisation, since a pure downscale of such potentiometers would include mechanical parts being too complicated to manufacture and handle in a cost efficient production process.
An additional problem with PJ 88 is that it is not possible to independently adjust an angular position of the user rotatable part where the switch function and the tactile feedback occur.